Acoustoelastic Effect of Rayleigh Surface Wave in Isotropic Material

The acoustoelastic effect is investigated for the Rayleigh surface wave propagating in a homogeneous isotropic material. The initial deformations considered are uniform and nonuniform only in the direction of depth. The formulas for the velocity change versus the change in the applied static stress are derived in the first-order approximation. The result for the uniform case, reducing to that of Hayes and Rivlin, exhibits no dispersion and the velocity change proportional to the principal strains. To be noted is the result that the Rayleigh wave becomes dispersive under the nonuniform stress state, depending roughly on the product of the wave number and the characteristic depth over which the stress varies. The dispersion is remarkable for the relatively low frequency and diminishes as the frequency increases. The analytical results are verified by measurements with mild-steel samples on the basis of the sing-around technique.